Badio beceiving cibcijtt



RADIO Ec'isIvmG' CIRCUIT Filed July 2.! 1920 swung- 5m 1 0 ammo g-17.1 926. I 1,596,3 V I 'A. H. TAYLOR RADIO RECEIVING CIRCUIT FIG. 5'

v A. H. TAYLOR 1,596,636 RADIO macmvius CIRCUIT Filed-July a. 1920 I 3 Sheets-Sheet '5 Patented Aug. 17,1926.

-hll'l" STE ALBERT HOY'I TAYLOR, or WASHINGTON, ms'rnror OFCOLUMBIA, assrono n To WIRED RADIO. mo, OENEW YORK, N. Y., A eonrona'non or DELAWARE.

RADIO RECEIVING CIRCUIT.

Application filed July 2,

My invention relates generally to direc tional radio receiving circuits and -has for an object thereof to produce a substantially perfect blind spot or direction of no signals.

Another object of my invention is to provide means whereby the blind spot may be rotated (in a horizontal plane) with respect to the vertical plane of the antenna.

Another object of my invention is to eliminate residual directional discrepancy in the linear collectors or antenna wires.

Still another object of theinvcntiou is to provide means whereby- ;lS \'ll1l1l0l rlcal capacities in the receiving set may be neutralized. A further object of my invention is to provide a circuit of this character by which it is possible to receive signals through an exceedingly strong local interference.

A still further 0b ect of the invention is to provide means by which it s possible to select the station from which it is desired to receive and practically eliminate other stations that may be transmittingat the same time and on the same wave length; 'and also to make such selectivity possible even in the presence of strong local interference.

The invention will now be described in detail, reference .bcing had to the accompanying drawings in which:

Figure l is a diagrammatic-view of tllu complete circuit, and

Figures 2 t0 8 inclusive are diagrams assisting in the explanation of the theory of the circuit.

\Vith reference to Figure 1, letters A, A,

- indicate two ordinary linear ground wire collectors or other forms of low horizontal antennae. The two collectors form a straight -line approximately at right angles to the direction from which maximum interference is to be expected.

'lhecollectors are connected to the primary L of the receiver in the usual manner, with the exception that there is a variable resistance R, 11, inserted in series with each wire, by which the intensity of the reeeived signal may be varied.

V The secondary of the receiver is of the usual type and is indicated by reference character L".

Connected across the primary L of the receiver is a resistance R and traveling over the same is a slider B. Connected with 1920. Serial No. 398.570.

the slider is an auxiliary adjusting circuit consisting of a variable condenser C and inductance c011 L ]O1I18(l In ser es'wlth ground G or its equivalent, a counterpoise. It 15 well known that to obtain the best'results with linear collectors the wires should be of a certain length, varying with the Wave length received, but as it is not possible in actual practice to vary the length of tho wire for a wide range of wave lengths, I accomplish thedesired result by the 1111110 tlnction of resistances It, K. As previously stated the resistances R, It also serve to vary the intensity of the received 'signal. Obviously, resistanceslt, R, could be omitted where the collectors are of the optimum' length for the wave length used. The resistance of It need not be great as I have found SQohnis suitable in practice.

I will now give thetheory of the action of my circuit, which theory will clearly show how a. substantially perfect blind spot may beobtained, how this blind spot may be rotated, and also how asymmetrical capacities in the receiving set may be neutralized.

First, directivity of a pair of linear collectors in substantially a straight line, one of which is connected to one primary bind ing post and the other to the other primary binding post of a receiver, is essentially the figure 8-shaped directivity as shown in Figure 2. This directivity is substantially the same as that of the loop and, just as in the case of the loop, it is foundin actual practice that the minimum is not absolute, but is disturbed by a residual effect which, in the case of the loop, is known as the antenna eifect'and should probably go by the :same name in the case of the pair of linear collectors. The receiving set itself having a certain capacity to earth, which may not be syn'imet-rically distributed, introduces this antenna effect which results in a slight blurring of the minimum as shown by the shaded areas in Figure 2. One of the purposes f the invention-herein discussed is to bring about an absolutely sharp minimum in order to completely'cxclude'powerful interferences from directions not coinciding with the direction of the signal. ith reference to Figure 1, it may be stated tha'tthe shunting of the moderately high resistance across directivity of the system but offers an adustable means of accentuating-the antenna the primary'does not materially change the v llO ill

the last one,

efl'ect in either right or left linear collector; Figure 3slioivs the nature of the dir'ectivity which may be expected when a linear collector otno great length is used connect d to one teriuinal'of the receiving. set and a ground conhection to the other terminal and on the assumption that'the antenna effect is approximately equal to the horizontal linear collector effect and that by some means their phases are properly adJusted. This type of directivity corresponds to that which is obtained with the herein discussed invcntion when the slider 13 is moved ,to the let t lllllld filld of" the resistance R.

This type of directivity may be called cardiac and is due to the compounding of a circular directivity shown in Figure 4, which is typical of an ordinary antenna, with the ligurefi'directivity whichlis typical of hcrizontal linear collectors and loops. There loes not appear to be an antenna in the system herein described, nevertheless, such ant enna is actually present. It must be remembered that any linear collector'will, in practice, he used either a few feet above the ground, on,the ground, or a few feet under the ground,-und that in all these ases, cvcn center of gravity ol the permanent ground (that is, permanent coiulucting shcet ol the earths surface). Figure 5 shows the general nature of the electric vector in a wave travcL me; over the surface of the ground. On account of the inclination -ol-this vcctor,-lit will be seen that it. has a weakhorizontal ooi'nponent but a strong vertical component. The vertical component is ordinarily used in antenna rece,'ition, whereas the horizontal component comes into play in the use of linear collectors placed sl'llisti'intially horizontal. For this reason it is always no -cssarv to use considerable amplilhialion when receiving from I horizontal collectors, or ncaiuy horizontal collectors, when the saunare oi" nmderato length. On account ol' th -v slight inclination ol the wave l'ront it will he sci-n liy rcl'crci'icc to Figure 5 that a horizontal coiirctor scvcral hundred loci. in l ngth is able to develop no more clor-lro motive l'orco l'roni lhc rcccptio'n ol' th \Vvuh horizontal component ol the electric vector than is a vertical antenna of only a low l ci. in l'iciglrl receiving llHf strong vertical coinponczit. ll', thcrcl'orc, a lincal collector, lor instance 2W) l'cct long hc only two l'cct above the permanent. ground (center of gravity of ground manducting sheet) the antenna cll'cct, which is not dircrtional, will be of the same order oiumgnitudc as -"ulinear. collector el'l'cct which is direct ional; Although the com ponents of the electric vector are naturally in phase; the resulting horizontal and \'crti cal components ot' olcctromotive l'orcc do not. necessarily produce currents in phase with each other, as this will depend upon the way 1 its actual level is abovie tho ar-ting to blur the'circuit is permittedto respond to these two electroinotive forces. Figure 6 shows the result-of combining a circular directive ity with ajfigure S directiVity, the circular directivity being the-antenna,efl'ect and the figure 3 being the lineal collector or 100) efiect, the intensities not being quite equa-. The cardiac directivity figure is the result. This then is the type of direotivity we may normally expect from 'a linear collector which is connected to one post of the receiver, the other post being connected to the ground, except in such cases where the linear collector is very long .in comparison to its height above the center of gravity of ground. Such a case'is actually observed in long wave reception with wires from 1,500 to 2,000 feet in. length. There has been in the past considerable dispute as to whether such a wire received stations better from the direction in which the ungrounded end'of the wire points or vice versa. The theory shows that it all depends upon the horizontal length of the linear collector used/and its height above the location of the center of gravity of permanent ground. Actually, there is probably always some ditl'ercnce, the antenna effect the minimum of theligurc 8 or normal linearcollector type of directivity and to give aslight tendency towards a cardiac form.

The invention herein described refers to a case where by the use of high amplification it is possible to utilize relatively short linear collectors and where, therefore, the antenna client in said collectors is of the same order ol magnitude asrcgular bi-dircctional or linear collector ,(similar to loop) cll'cct. Longer wires might be used it the antenna cll'cct is intentionally "accentuated either by lifting the v to them a. vertical section proper dimensions.

Wit h rcl'crr-n o to Figure I, when the slid- 1'1 ll is pushedcompletely to the left, the primary circuit is traversed by two curm nts, onc ol' which passes l'roiu'tlic right hand lincar colle tor to the lcl't. hand linear i'l ll(' lr)l":-Hl(l which corresponds totho figure 8 dirc tivity, and the other which passes l'roinlhc right-'haiul linear collector-lhrough the primary ol' the receiver and thence thru the auxiliary adjusting circuits tuned by the rondcnscr L "and inductam-e following it, to a counterpoise or ground conl'ic'ction. 'l'his second, current is due to the dill'crcncc ol' potential between the linear collector and ground, and its phase is adju table by the condenser C independently ol the phase adjustment ol the other current coniporuant. it is thus seen that all the elements are pres out which are necessary to get a coiubinzv tion of circular dircctivity and ligurc 8 shaped dircctivity which combination is the cardiac directivity' The circulation of curta-ntcnna) of the linear collectors or .by attaching Lil) rents in this case is such as to make the circuit blind to the right; (See Figure 3).

The left hand linear collector discharges its component of current due to antenna 5 efi'ect directly through the tuned adjusting circuit to counterpoise or ground, only a small portion of it passing back through the primary to the other linear collector and thus by capacity effect to ground. Nevertheless, this small portion may be objectionable for signals from certain directions and for powerful local interferences. A certain amount of regulation is obtained by the use I f the resistance R in series'with the linear collectors. If the slider B is now moved ,to the op site end, namely to the right, the left han linear collector discharges its antenna efiect through the primary and since the phase of the current due-to the other effect, i. e., regular linear collector figure 8 shaped directivity, is opposite to What it is for the right hand linear collector, it is evident that the cardiac figure of resultant directivity will be reversed as shown in Figure 7; If the slider B is placed in the center, both linear collectors get rid' of the antenna effect currents equally and symmetrically through the tuned h'y-pass and, --as far as the primary is concerned, mutually oppose each other so as to cancel except in so far as there may be, as outlinedabove, unsymmetrically distributed capacities in the receivin set. By deviatingthe slider B slightly one way or the other from the center, suflicient asymmetry in the antenna etfect currents may be arbitrarily produced so as to accurately offset asymmetrical capacities in the receiving set, thus making the minimum exceedingly sharp. It then the slider B be started at the left, the circuit receives strongly from the left; it also receives very well from directions at right angles to the linear collector system and on either side of it, but it is nearly blind to signals coming from the right. This type of directivity, as the slider is moved, changes slowly over .until when the slider isv near the middle, the directivity is sharply figure 8. receiving equally well from right and left but nothing at right angles. 11 the motion is then continued the cardiac figure appears again, reversed from its original position and the circuit receives best from the right. fairly Well from directions at right angles to the linear collector system, but has a blind spot to the left. It is evident that between the extreme positions and the middle that all lcinds of intermediate types of directivity may be obtained. The action proluibly somewhatn' orc complicated than herein described. but in actual practice it is seen that the blind spot will wander around from one point of the cornpass. to another 180 degrees distant by-simply moving the slider and adjusting the directivity with,

and at right angles to the system. This is.

similar to what happens when an antenna 1s loosely coupled to a loop, said antenna .producing a weaker signal than the loop.

This case is shown in Figure 8 and gives a figure differing only slightly fromt 1e cardiac shown'previously and containing two blind: spots, neither of which is opposite to the' direction of maximum reception. It is evident that two loops can be used with this circuit, provided that their dimensions are such that they simulate the relative amount of antenna eflect and bidirectional effect of the linear collectors. relatively tall and number of turns.

narrow and with a small loops and will not be herein repeated.

From the above description it is clear that I am able, by means of theauxiliary adjusting' circuit, to produce a substantially perfoot blind spot at right angles to the direction of the linear collectors, when the slider B is near the center of the resistance R; that by placing the slider near either of its extreme positions the circuit may be made blind to either the right or the lett: that for intermediate positions of the slider the blind spot will be rotated to intermediate positions. It follows thcreforeT'that it several stations at dill'crcnt points of the compass are transmitting at the same titre and on the same wave length. then by, means of the above described adjustments it is possible'to favor the station it is desired to copy and to substantially eliminate the others; and further, this result may be accomplished through a strong local interfercncc.

Another feature of my invention is the elimination of residualdire tional discrepancy. lt is impossible in practice to lay the linear collectors at. absolute. right angles to the direction of n'mxin'uim int rference. and it also is impossible to have the wires in a perfectly straight line. There results. of course. an imperfect blind spot. The flexibility of dirc tivitv obtained by the use of my auxiliary adjusting circuit. permits the 1 cquivalfuit of a slight rotation of the collcctors iv icrcby any r idual directional (liscrepancy is eliminated.

'hile I have shown and described my invention as applied to linear collectors in underground systems, this is not to be conand Such loops will be The argument of the theory is essentially the same when applied to sidered in a limiting: svnse us: the circuit is equally well adaptable to uxc'in cmmm'tiqn with either loops or linear ('ulle'tors located underground, unde water, on the ground. 5 or above the ground.

Having thus" described nq invention what I claim and desire to For-urn by Lctters latent 0f the Unifed States is:

'1. A directional antenna and means associated therewith for producing a sEuhs-tantially perfect blind spot comprising an uuxil- -und -a rusistuni-n with iury circuit associated with said antenna variu'hhe crmtuct (10nnerting said antenna and auxiliary circuit.

2. A dirm-tiunal anfenna .and adjusting 15 means associatml therewith for neutralizing asymmetrical capacities in the receiving set g omprisin'g an auxiliary cirruit associated with said antenna, and a resistance with variable contact connecting said antenna and auxiliary circuit.

ALBERT HOYT TAYLOR. 

